Cytogenetic analysis of Bienertia sinuspersici Akhani as the first step in genome sequencing.

Background: C plants are efficient in suppressing photorespiration and enhancing carbon gain as compared to C plants. Bienertia sinuspersici Akhani is one of the few species in the family Amaranthaceae that can perform C photosynthesis within individual chlorenchyma cells, without the conventional Kranz anatomy in its leaf. This plant is salt-tolerant and is well-adapted to thrive in hot and humid climates. To date, there have been no reported cytogenetic analyses yet on this species.

Objective: This study aims to provide a cytogenetic analysis of B. sinuspersici as the first step in genome sequencing.

Methods: Fluorescence in situ hybridization (FISH) karyotype analysis was conducted using the metaphase chromosomes of B. sinuspersici probed with 5S and 45S rDNA and Arabidopsis-type telomeric repeats.

Results: Results of the cytogenetic analysis confirmed that B. sinuspersici has 2n = 2x = 18 consisting of nine pairs of metacentric chromosomes. Two loci of 45S rDNA were found on the distal regions of the short arm of chromosome 7. Nine loci of 5S rDNA were found in the pericentromeric regions of chromosomes 1, 3, 4, 6, and 8, which also colocalized with Arabidopsis-type telomeric repeats; while four loci in the interstitial regions of chromosome 5 and 8 can be observed. The single locus of 5S rDNA that was found in chromosome 8 appears to be hemizygous.

Conclusion: The FISH karyotype analysis, based on the combination of rDNAs, telomeric tandem repeat markers and Ct DNA chromosome landmarks, allowed efficient chromosome identification and provided useful information in characterizing the genome of B. sinuspersici.